The establishment of a shared analytical ultracentrifuge facility would enhance and expand the research programs of a number of NIH supported researchers at UMDNJ-Robert Wood Johnson Medical School. Some of these researchers are biophysically oriented, while others with a molecular biology focus have increasingly complemented their functional studies with structural characterization, supported by the strong structural biology laboratories in our scientific community. The sedimentation studies proposed in this application would provide information on molecular mass, shape, stoichiometry, and intermolecular interactions in systems ranging from model triple-helix and coiled-coil peptides to regulatory proteins, transcription and elongation factor complexes. The interest of these investigators in applying sedimentation methods to their research projects has been driven by two factors. Firstly, the recent advances in analytical ultracentrifuge design and optics, as well as the automation of data acquisition and analysis, has made the method accessible to motivated scientists as well as dedicated experts. Secondly, as a result of efficient expression systems, solid state peptide synthesis, and improved purification methodologies, the quantities of purified molecules and complexes necessary for analytical ultracentrifuges with improved sensitivities have increasingly become available. The results of the proposed studies using sedimentation, with its rigorous thermodynamic basis, will provide information complementary to existing methodologies and can be integrated with the molecular structure data obtained from NMR spectroscopy and x-ray crystallography. In addition, it is the technique of choice for studies on very high molecular weight complexes and for systems where other methods have yielded ambiguous results. The need of these researchers for an analytical ultracentrifuge cannot be met under existing conditions. There is no academic institution in New Jersey that has such instrumentation and collaborations have provided only limited access to sedimentation studies. Several investigators on this application have been involved in productive collaborations with ultracentrifuge experts at national facilities or in private laboratories. But such collaborations are hampered by their long distance nature, the numerous projects ongoing at each center, and the barriers to exploring new areas or following up interesting observations or problems. No user on this application requires more than 15-20 percent of the time on an analytical ultracentrifuge, so that its purchase by any one individual cannot be justified, and yet the presence of this instrument would greatly strengthen the research programs of all users. A shared analytical ultracentrifugation facility would strengthen the research projects of Robert Wood Johnson Medical School researchers by allowing them to utilize this powerful technique.